Hot-carrier (HC) degradation was compared in three kinds of intermetal oxide structures : in a single layer of tetraethoxysilane (TEOS) based plasma-enhanced silicon dioxide (PETEOS) structures, in PETEOS-based spin-on glass (SOG) etchback structures, and in PETEOS-based SOG nonetchback structures. HC degradation was found to be enhanced in SOG nonetchback structures rather than in SOG etchback structures. HC degradation in SOG etchback structures is almost the same as in a single layer of PETEOS even though SOG remains over the gate of the transistor measured. Next, the influence of water-related species in intermetal oxides on HC degradation was investigated. The PETEOS is blocking H2O which diffuses from the SOC in the SOG etchback structure. However, H2O diffuses through the PETEOS in the SOG nonetchback structure with a large amount of SOG. Moreover, we understand that a little OH- released from PETEOS in the final annealing most likely enhances HC degradation.